Unravelling a photoinduced compressive lattice response in the canonical Mott insulator (V1-xCrx)2O3

This proposal aims at determining the nature of lattice strain, compressive vs tensile, following the ultrafast photoexcitation of hot carriers in Mott insulator (V1-xCrx)2O3. Our μ-XRD mapping on (V0.95Cr0.05)2O3 thin films after an electric field-driven insulator to metal transition indeed revealed a compressive lattice response. As electric field and light pulses are both prone to generate hot carriers, we might expect that photoexcitation would also induce a compressive lattice response in (V1-xCrx)2O3. However our recent time-resolved XRD study of (V0.95Cr0.05)2O3 films at ID09 revealed a tensile rather than compressive effect. To clarify the situation, we propose to work in parts of the temperature-x phase diagram more prone to reveal this sought photoinduced compressive effect. Overall this study might challenge the paradigm by which photoexcitation of matter always leads to a thermally-driven expansion, and suggest that Mott physics can lead to a reverse compressive behavior.